With record UV measurement, astrobiologists determine parts of Earth less habitable than thought

In a surprise discovery, a group of scientists from NASA and the SETI Institute claimed they were looking for Mars-like habitats on Earth when they measured a UV index of 43.3– a world record – atop a 19,432 foot volcanic peak in Bolivia. Levels of 11 or 12 are considered hazardous.

The scientists had been going through some old data and found the UV spike had occurred in 2003. They attributed it to a combination of storms and fires depleting UV locally, ozone-depleting chemicals migrating from Antarctica, and a solar flare.

That scary sounding number raised many questions. Where and how is ultraviolet normally monitored? How have UV levels changed since the Montreal Protocol mandated the phasing out ozone-depleting CFCs? Isn’t the situation supposed to be slowly improving through this century?

How much does high altitude matter and what would be considered normal at 19,423 feet? What is a typical summer UV index in Antarctica, under the ozone hole?

And to get back to basics, what measurements go into calculating the UV index? Is it a linear scale?

Earlier studies by Richard McKenzie, a scientist at the National Institute of Water and Atmospheric Research in New Zealand, also found that the high Andes in Peru, Bolivia, Chile and Argentina regularly hit UV index levels higher than 25.

In the Andes, intense tropical sun, high elevation and naturally low ozone levels combine to boost UV radiation to record heights. But modeling of atmospheric conditions in December 2003 suggests an unusual combination of factors combined to send protective ozone levels plummeting, the researchers reported.